The structural and surface properties of sulfated gamma-Al2O3 prepared by hydrothermally aging precipitates obtained from aluminum sulfate and ammonia have been studied. The Lewis sites are formed on coordinately unsaturated fourfold alumina. No pentacoordinated aluminum has been found, probably as a consequence of the aging process. Residual sulfate is distributed among several species characterized by their desorption temperatures. Bronsted sites of high strength are probably located on sulfate species desorbing between 900 and 1000 degreesC. They may have the following schematic structure (O=)(2)S(-OH)(-O-Al). The decomposition of 4-methylpentan-2-ol shows clear differences according to the types of acidity present on the surface. The sulfated aluminas have favorable textural properties: pore size congruent to 50 nm and specific surface area congruent to 200 m(2)/g stable up to more than 700 degreesC. (C) 2003 Elsevier Inc. All rights reserved.